Even as EVs begin to encroach on ICE cars, the development of fuel-burning engines hasn’t stopped. With almost 150 years of development in the Otto cycle internal combustion engine, you may think there’s not much left to do—but you’d be wrong.
One company is looking to the past, to bring ICE into the future. By rethinking the venerable two-stroke engine, we might just see ICE vehicles hold their own against EVs for some time yet.
Two-Stroke Engines Are Awesome—Until They Aren’t
Yes, this is about atwo-strokeengine being a potential competitor for EVs. As mad as that may sound, you’ll understand why soon enough, but I have to spend a smidge of time talking about what a two-stroke engine is.
Most modern gas-burning engines are four-stroke. So they only produce power once every four strokes of a piston, with induction, compression, combustion (power), and exhaust all happening on an independent stroke of a given piston.
A two-stroke engine, on the other hand, combines these phases into only two strokes by using a clever design where the piston covers the intake and exhaust ports at different points in the cycle, allowing the engine to produce power with every second stroke of the piston. This has a dramatic effect on power density compared to a four-stroke engine with the same displacement.
It’s why two-stroke engines dominated racing for so long, as the four-stroke alternatives just couldn’t keep up!
Unfortunately, there are three major downsides to two-stroke motors:
This might not matter all that much in a motorsport race where the engine will often be rebuilt, or for a weekend dirtbike that doesn’t run hundreds of miles every day, but for day-to-day motoring, four-stroked have essentially made two-stroked extinct.
Maintenance and fuel efficiency aside, what really did the two-stroke in was stricter emissions regulations. Because the typical two-stroke design wastes so much unburnt fuel (and don’t forget those additives) it’s basically impossible to meet those standards, and so the design was phased out.
Even modern diesel engines are cleaner by comparison, and a modern four-stroke might as well be putting out fresh mountain air compared to two-stroke engines. Which means that any modern take on the two-stroke design has quite the mountain to climb.
A New Two-Stroke Design Could Be the Best of Both Worlds
The thing is, those shortcomings of the two-stroke design are a result of certain aspects of that design. So what if you could design an engine that made power on every second stroke, but wasn’t fuel inefficient, didn’t pollute the air (as much), and would last just as long as a four-stroke, if not longer? It sounds like a pipe dream, but a company calledAlpha-Otto Technologieswith apatented new engine designthinks they might have cracked it.
It’s called the REV Force™ Engine Architecture and basically solves (on paper) every design shortcoming of two-stroke engines as we know them. Alpha-Otto makes some big claims about this motor:
That sounds like something Doc Brown would bring back from the future in his flying DeLorean, but it’s a real engine that actually runs. At least insofar I’ve seen videos of it.
The big innovation (though not the only one) when it comes to this design includes a rotary exhaust valve, which prevents any unburnt fuel from leaving the engine through the exhaust. It also means you don’t need those bulbous exhaust chambers synonymous with two-stroke engines of the past, which used reflected pressure waves to combat the leaky exhaust valve issue.
Likewise, this new design uses a supercharger for air-intake, so you have a fast and efficient cycle to clear exhaust gases, and get fresh air for the fuel and air mix. Thanks to the REV Force design, the engine can be conventionally lubricated. Which means no oil is burnt, because no oil additives are needed. That conventional lubrication also means that engine wear is like that of a four-stroke, not a two-stroke.
These improvements don’t just mean much higher power density, but that the engine can rev higher than traditional two-strokes. The existing prototype that we’ve seen is an inline two-cylinder engine with 578CCs of displacement. The engine weighs around 110lbs. It’s small, it’s light, and according to Alpha-Otto, it produces 220HP!
I strongly recommend checking outdriving 4 answersand his YouTube video on the REV Force engine. He goes into very precise detail about how the engine works, and, of course, there are lots of animations and videos that make it simple enough so even I can understand it.
EVs Might Have Some ICE Competition Again
Alpha-Otto is looking for funding to turn their prototype into a mass-production engine ready to go into vehicles, and I personally hope they succeed. The idea of a small car or motorcycle that puts out over 200HP and can run on anything that burns is highly appealing to me, but it could also offer a real alternative or supplement to EVs.
Technology like this also benefitshybrid designs, and with the rise of fuel sources that are carbon-neutral or don’t contributedangerous emissions, an engine that can efficiently use those fuels is crucial.
